Hi.
First thing turn machine over & turn the 3 plastic screws near brush roller to unlock position then lift off the sole plate.
If you can see the motor spindle just fit new belt over roller then spindle.
If you cant see the spindle then you have a clutched model machine this is more difficult to replace the belts there are 2 of them.
Try this site for help.
http://dysonmanuals.inc.io/
Chris
November 2007